Civil Engineering - Theory of Structures - Discussion

28. 

A rolled steel joist is simply supported at its ends and carries a uniformly distributed load which causes a maximum deflection of 10 mm and slope at the ends of 0.002 radian. The length of the joist will be,

[A]. 10 m
[B]. 12 m
[C]. 14 m
[D]. 16 m
[E]. 18 m

Answer: Option D

Explanation:

No answer description available for this question.

Suhasini said: (Feb 3, 2015)  
Max deflection = 5wL4/384EI.

Slope = wL3/24EI.

w = 24EI*slope/L3.

Max deflection = 5*(24EI*slope)*L4/(L3*384EI).

Therefore, L = max deflection*16/(5*Slope).

= 10*16/(5*0.002) = 16000 mm = 16 m.

Chhaya said: (Oct 5, 2017)  
Thanks @Suhasini.

Asay said: (Nov 21, 2017)  
Deflection=5wl^4/384EI=10mm.
=====> EI=5wl^4/384*10 -----> (1)
Slope=wl^3/24EI=0.002mm
=====> EI=wl^3/24*0.002 -----> (2)
Comparing eq (1) & (2)
5wl^4/384*10=wl^3/24*0.002
l=384*10/5*24*0.002
l=384*10*1000/5*24*2
l=16*1000mm
l=16m.

So ,
The length of the joist will be =16m
(Option D) is correct Answer.

Pawan said: (Jun 16, 2019)  
Thanks @Suhasini.

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